The usual way prior to this invention of connecting electrical power cables entering a building and fanning them out to the various secondary service disconnects in the building is by the use of clamping means, such as multiple split-bolt connectors into each of which one phase conductor of the power cable is inserted and is clamped in contact with one or more wires leading to a sub-disconnect box or to one or more service circuits. At each such conection, the split-bolt connector is screwed up tightly on the various conductors clamped therein. Then the split-bolt connector is padded to cover sharp edges thereof, and then the padded joint is heavily taped to provide the necessary insulation. These joints are made in an electrical junction box in the shape of a trough, the trough having attached ends and a cover which is screwed to flanges extending around the edges of the trough and end plates. It is not only a laborious job to make a joint using a split-bolt connector and tape, but the joint, when completed, suffers from serious defects. One defect is that the joint is not accessible under the tape so that the circuit wiring cannot be easily altered, for instance, to add new circuitry thereto. A much more serious maintenance problem, also attributable to the inaccessibility of the taped joint, is that the split-bolt joint can not be periodically tightened on the wires without turning off the power and removing the tape to reach and tighten the bolt clamp.
Periodic tightening of the joints is necessary to prevent loosening of the joint due to heat expansion and contraction. As heavy electrical loads are drawn, he circuit conductors heat and expand. When the load is reduced, they cool and contract, leaving a looser joint. Over a period of time, a joint can be loosened to such an extent that it develops a resistive spot where a great deal of heat builds up, sometimes causing a fire. The present invention provides an accessible terminal block for terminating power lines while facilitating the periodic maintenance steps of tightening of the wire securing screws, this terminal block also facilitating the adding of additional circuits thereto.
The prior art shows a great variety of screw type terminals mountable in junction boxes, for example, U.S. Pat. No. 2,863,935 to Barina issued Dec. 9, 1958, and German Pat. No. 1,199,355 to Knappe issued Aug. 25, 1965.